Pasteurization of milk



Nov. 30, 1937. E, GETCHELL 2,100,326

PASTEURIZATION OF MILK Filed March 21, 1936 2 Sheets-Sheet l WaterCooled INVENTOR BENJAMIN GETCHELL,

f ORNEY NOV. 30, 1937. H LL 2,100,326

PASTEURIZATION OF MILK Filed March 21, 1936 2 Sheets-Sheet 2 Hm: 2a-

-220" no m.

INVENTOR BENJ GETCHELL,

%'NEY Patented Nov. 30, 1937 UNITED STATES PATENT OFFICE PASTEURIZATION-OF MILK necticut Application March 21, 1936, Serial No. 70,170

8 Claims.

My invention relates to a system and apparatus particularly forpasteurizing milk by the action of electricity.

The main object is to provide a practical, reliable and efficient systemembodying relatively simple mechanism.

Another object is to provide a system in which the apparatus can be setfor one or more predetermined rates of delivery so as to synchronize themilk flow with a bottling machine.

The system has also-been designed to control the treatment temperaturewithin a predetermined narrow range and prevent the passage through thesystem of milk which has not been properly pasteurized.

I have also sought to provide a system which is wholly automatic afterit has once been started in operation and which will automaticallyopcrate to compensate for variations in the temperature of the suppliedliquid, the conductivity of the supplied liquid, and the roomtemperature and variations in the line voltage.

Although the apparatus was designed primarily for the pasteurization ofmilk, it will be understood that certain features ofthe invention areapplicable to similar electrical treatment of other liquids wheretemperature control is essential. T

In describing the construction and mode of operation, I will forsimplicity generally refer to the system and apparatus especiallydesigned for the treatment of milk.

The system embodies an electrode chamber and a circulating systemthrough which the liquid is forced by the action ofian electricallymotor driven pump. This circulating system in cludes a heat exchanger orregenerator through which the cold milk is forced andwhich is subject tothe action of the heated milk so that the outfiowing heated milk iscooled and the inflowing milk is' preliminarily heated by the treatedmilk.

The temperature of the treated milk is controlled by varying theelectrical input to the heating chamber by increasing or decreasingresistance in series with the electrodes of the heating chamber. Thisresistance may be arranged in three sections, one of which is normallyin the circuit with the electrodes of the heating chamber, and the othertwo are normally out of circuit with the electrodes. Under abnormalconditions any one, two or three of these resistance sections may beautomatically cut in or out of the heating circuit as may be requiredand which will be hereinafter set forth. The

flow of milk through the system may be controlled by the manualoperation of a hand valve so as to synchronize with the speed of thebottling machine to which the treated milk is fed.

Variations in the temperature of the raw milk, in the electricalconductivity of the milk, in the room temperature or in the line voltagewill be compensated for automatically by increasing or decreasing theresistance in the heating circuit.

For this purpose, an electrical control device is employed, having atemperature sensitive element subjected to the milk immediately after itleaves the electrode chamber, and switch elements such, for instance, asare more fully shown in my application, Serial Number 752,223, filedNovember 9, 1934, the action of which controls the starting and stoppingof the pump motor and the cutting in and out of the resistance sectionsin the electrical circuit.

Fig. 1 is a diagrammatic view showing the liquid circulating system.

Fig. 2 is a diagrammatic view showing the electrical control system.

The liquid to be treated is contained in one or more reservoirs such as5 and 6,,one of which may contain, for instance, raw milk and the othera liquid for cleaning the circulating system or for facilitatingthestarting of the action of the apparatus without wasting milk.

The pump I is preferably of the rotary type so designed that iquid can.flow backward through it when the pump is stopped.

A 3-way valve 8 controls the selection of liquid. The electric motor 9,which drives the pump is of the type which is self-starting when thecurrent is turned on.

The circulating system includes the conduit ID, the regenerative coils Il the heating chamber l2, the holding chamber l3, the spreader or sprayhead It, and the collecting trough l5, which discharges through the pipeIB to the bottling machine or other disposal point. The hot milk isallowed to run down over the surface of the regenerative coils by whichit is cooled and then over the refrigerating or cooling coils II tobring the temperature of the milk down to that required. The rate offlow of the liquid through the system is controlled by a manuallyoperablevalve l8.

To prevent the overheating of the electrodes,

themselves, I provide suitable water cooling means such as shown anddescribed inmy former application above referred to. The auto maticcircuit changing device 2! is actuated by a temperature sensitiveelement 22 arranged at the I the outlet of the holding chamber i3 ismeasured and recorded by a suitable instrument 2 5.

The temperature of the raw milk supply is supposed to be approximately50 F. but may vary from 35 F. to F. without interfering with theoperation of the system. The requirement for pasteurizing milk by thehigh temperature method is 160 F.'held 15 seconds. The temperaturecommonly used in this process is 162 F. so as to provide a reasonableleeway for variation without going below the 160 limit. In pasteurizingother liquids, or milk for other purposes, it may be desirable to usehigher temperatures than those previously specified, and the system isso constructed that any pasteurizing temperature above 160 may be used.7

The heat exchanger or preheater is preferably designed to raise thetemperature of the milk to approximately before it is electricallytreateds In such a case, the electrode chamber will be so designed as toadd approximately 35 to the temperature. When pasteurizing milk, it iscustomary to immediately chill it below 50 by means of the refrigeratingor cooling unit. The cooling liquidto be employed will depend, ofcourse, upon the temperature requirements. At certain times, or incertain places, it may be necessary to employ brine, or otherrefrigerant, while at'other times or places, ordinary tap Water may besumciently cold.

The system requires alternating current but does not require highvoltage. It is designed for use on standard commercial current such as220 volts A. C. The electrodes of the heating chamber 82 are adapted tobe connected in the main line in series with a number of resistances.

In describing the following electrical system, it should be noted thatfor the purpose of uniformity and simplicity, I have shown the movement'of all relays and contactors as being downward when energized, andupward when unenergized.

The electrical system includes the following parts: I m

- There may be a main line disconnect switch, (not shown) through whichan electrical power supply such as 110/220 volt three-wire, singlephase, alternating current is furnished to the system. 29 is amanually-operated switch, which controls the power furnished to the pumpmotor circuit. It also determines the energization of the line side ofcontrol switch 30.

El is a temperature controlled contactor. This contactor is operated bymeans of a bulb 22 in the milk flow just above the heating chamber andis responsive to variations in the temperature of the milk as it leavesthe heating chamber. In this contactor are three contacts-Zia whichactuates a circuit guarding against milk-flow below Zlb to correcttemperature if it drops onehalf degree or more below the predeterminedpasteurizing point, and Me to correct temperature if it raises one-halfdegreeor more above the predetermined pasteurizing point. 2! has amanually adjustable means (not shown) for setting the pasteurizingtemperature at whatever point may be desired above 160". When thepasteurizing temperature is set above 170, contact 2 l a is inoperative.

i2 is a heating chamber, which is supplied with electrical powercontrolled directly by means of a resistance system 26, 25 and 21 andindirectly by means of the contacts which'are actuated by respectiverelays 32, 43, 46 and i5.

36 is a water actuated relay, which is in circuit with the controllingwinding of a magnetic contactor 32, which controls the power furnishedto the heating chamber circuit. Failure of cooling water to flow overthe electrodes of the heating chamber will cause this relay to open thecontrolling magnet circuit'of contactor 32 and thus interrupt the supplyof power to the heating chamber l2, due tothe opening of the controlledcontacts actuated by contactor 32.

35 is' a milk actuated relay, which is in series with the controlling'circuit of an alarm relay 31. If the supply of milk in the raw'milktank drops below a predetermined level, it will cause the opening-of themagnetic circuit of relay 3?, allowing an alarm 35 to notify theoperator.

9 is a pump motor which is under manual control of switch 29 and alsounder automatic control of relay ll. g

40 is an auxiliary electrode located in the milk stream just above theheating chamber and ad jacent to bulb 22 of temperature contactor 21!.

It is in series with the controlling circuit of relay ill and if it isimmersed in a fluid so that current is flowing by means of thiselectrode when contact Zia closes, the circuit is completed through thecontrolling winding of relay All to electrode ll) and thence through thefluid to ground. This causes relay ll. to open the pump motor circuitand thus stops the fiow of milk. If there is no conducting fluid incontact with the electrode-15, the circuit including the controllingWinding of relay ll will not be completed and the pump will not stop.

Resistances 26, 25 and 271 are connected in series and are under theautomatic control of magnetic contactors 63, M and 45 respectively.These resistances are thereby automatically cut in or out of the circuitsupplying power to the heating chamber i2, as occasion may demand and ashereinafter explained.

32 is a magnetic contactor in the circuit supplying power to the heatingchamber l2. This contactor is under the automatic control of thewater-actuated relay 34, as hereinbefore ex-' the contacts of contactor43 open, thus inserting resistance 26 into a series circuit with theheating chamber in order to reduce the current and prevent over-heatingof the milk during this period.

- 44 is a magnetic contactor Which is under the control of relay 56,which latter normally holds the contacts of M in an open position.Contactor 4G, in turn, controls resistance 25 and normally keepsresistance 25 in series circuit with the heating chamber i2. If thepasteurizing temperature drops one-half degree below the setpasteurizing point, 2! closes the contacts Zib, which allowstheenergization of relay 5!). Relay 58, in ,turn, allows theenergization of magnetic contactor id, which closes its contacts andshunts resistance 25 out of the series circuit with the heating chamberl2, thus increasing the power reaching chamber l2 and causing the actualpasteurizing temperature to rise.

- 45 is a magnetic contactor which is under control of relay 52, whichnormally holds the contacts of 45 closed. Contactor 45, in turn,controls resistance 21 and normally holds it out of series circuit withthe heating chamber l2. If the temperature of the milk rises one-halfdegree above the set pasteurizing point, 2| closes the contacts 2lc.

This allows the energization of relay 52, which opens the magneticcircuit of contactor 45, causing its contacts to open and introduceresistance 21 into series circuit with the heating chamber. This lowersthe power supplied to the heating chamber and causes the pasteurizingtemperature to be reduced.

Magnetic contactors 44 and 45 are also under automatic control of relay4! in the same manner as described for magnetic contactor t3, and whenthe pasteurizing temperature drops below the limit, and the pump stops,contactors M and '35 will open their respective contacts, introducingresistances 25 and 21 in series with resistance 25 to assist in reducingthe power sup plied to heating chamber i2.

To start the system into operation, either one i of two methods may beemployed, the first and preferable of which is by the use of a solutionof salt in water of about the same electrical conductivity as the milk.In this method, the temperature controller is set for pasteurizingtemperature above to prevent the pump from stopping on flow temperaturesbelow 160. Valve 33 is set to permit the fluid from the saline solutiontank to flow through the system. Valve it is set to approximately theflow desired. The valve supplying electrode water is turned on for thepurpose of keeping the electrodes cool during operation. The waste waterfrom the electrodes actuates the water relay 34 so that when controlswitch 3G is turned on, circuit will be established through magneticcontactor 32 to supply power to the electrode chamber.

Switch 29 is now closed, which starts the pump.

and supplies power to the line side of switch 3t. Switch 3G is nowclosed, which actuates the control circuits and causes power to besupplied to heating chamber i2. Fluid leaving the chamber one-halfdegree or more below the pasteurizing setting causes 2! to contact at2th. This energizes relay 59, which in turn energizes magnetic contactor4 causing it to close and shunt resistance 25 out of circuit withheating chamber l2. Resistance 25 is also shunted out of the heatingcircuit because magnetic contactor A3 is held closed by relay M.Resistance 2? is also shunted out of the heating circuit becausemagnetic contactor 45 is held closed by relay 52. Thus during the periodof bringing the temperature from cold up to the pasteurizing point, fullpower is supplied to heating chamber 32. The fluid passing throughheating chamber i2 is gradually raised in temperature. and is passedover the regenerative coils ii. This results in raising the temperatureof the cold fluid as it enters heating chamber i2 and, in turn, raisesthe temperature as it leaves the heating chamber. This increased heat,in turn, raises the regenerative temperature still further and the cyclecontinues until the temperature of the treated fluid reaches thepasteurizing temperature as set at 2 i. 2! may now be set at apasteurizing temperature of" 162. This will cause contact 2H) to openthe circuit of relay .50. Relay 50, in turn,

. will open the circuit of contactor 44, causing its resistance 21 intocircuit with the heating chamber. The insertion of resistances 25 and 21into the heating circuit reduces the power to heating chamber l2 and thepasteurizing temperature will rapidly drop until it reaches withinone-half degree of 162, for which 2| is set. At this time, contact 2 towill open the circuit of relay 52, causing its contacts to close andenergize magnetic contactor 45, causing its contacts to close and shuntresistance 21 out of the circuit to heating chamber 12, thus increasingthe power to l2 and preventing a further drop of temperature. Thetemperature of the treated fluid will nowstabilize at 162 and anyvariation one-half degree above or below that point will causeresistances 25 or 2i to be cut in or out of the circuit to correct thetemperature to the set point. Valve 3 may now be thrown over so as tocause the milk to flow from the raw milk tank and follow the salinesolution through the system, thus driving all of the water out of thesystem and establishing a steady flow of milk. As soon as this is accomplished, the milk is led to the bottling machine by means of conduit it.

If for any reason the temperature of the milk rises or lowers one-halfdegree above or below the pasteurizing temperature, resistances or i'2'] will be automatically cut'in or out of the circuit to correct same,as previously described.

If due to a sudden change of raw milk temperature, drop of voltage, orchange of speed of flow, the pasteurizing temperature drops below 160,2i will contact at 2 la, establishing a circuit through relay ii toelectrode fit to ground. This causes relay M to open the circuit of thepump motor, thus immediately interrupting the flow or" milk through thesystem. The milk will then flow back by gravity through the electrodechamber for re-heating. Relay 4i also opens the circuit of contactors'33, Ml and 55, causing resist ances 2B, 25 and ti to be thrown intocircuit with the power to the heating chamber I2, thus reducing thepower through this chamber and preventing excessive over-heating of themilk during its backward flow. As soon as all of the milk below 169temperature, that attempted to pass out of the heating chamber, isreturned the change in temperature of bulb 22 will cause 2i to open thecontact Zia, which will interrupt the circuit through relay Ql. Thiswill allow the pump to resume operation and will restore resistances 25,25 and El into their normal circuit position.

If due to radiation of heat, all the milk up to the spreader pipe hasdropped below 160, it will all be returned through the heating chamberl2 without causing Zia to open.

If this happens, as soon as all of the milk has returned through theheating chamber G2, the circuit from electrode ll] to ground will bebroken 'due to absence of milk at this pointyand that circuit change inturn, will cause relay ll to reclose the pump circuit and cause the pumpto start.

If for any reason the cooling water ceases to flow over the outside ofthe electrodes of heat- .ing chamber l2, the circuit of magneticcontactor 32 will be broken at 3 causing'32 to open and interrupt thesupply of power to the heating chamber l2. This, in turn, will cause asudden drop of pasteurizing temperature, which will.

cause 25 to contact at Zia, and stop the pump, as previously described.When all of the milk has been returned to the heating chamber, aperiodic succession of starting and stopping will occur without furtherheating of the milk. This will notify the operator that something iswrong. As soon as the cooling water flow is restored, relay 3 3 willrestore the circuit to magnetic contactor '32, which will close andagain supply power to the heating chamber 92 and operation willautomaticaly be re-established, as previously described.

When the supply of raw milk reaches a predetermined low level in the rawmilk tank, relay 35 will open, causing relay 3? to close its contactsand start the alarm 3! into operation, noti fying the operator that hemust either replenish his raw milk supply or prepare to shut down theplant.

The process of shutting down the plant is the reverse of starting, andis accomplished simply by throwing the three-way valve 8 in positiontosupply saline solution to the pump. This solution follows the milkthrough the plant, driving it all out, at which time the controls may bethrown oii and the plant shut down.

The second method of starting is to start directly with the raw milk. Inusing this method, valve 8 is thrown into position to feed raw milk intothe system. Electrode cooling water is turned on, as before, temperaturecontroller ,2! is set at the desired pasteurizing temperature of 162,switch 29 is closed, starting the pump, and switch 30 is immediatelyclosed, which will put into operation the control system. The pump willoperate until the milk reaches electrode 60. The temperature of thisfirst flow of milk will be far below the pasteurizing temperature due tothe fact that regeneration of heat has not yet been established.Therefore, 2| will be in contact at 2la. Relays 50 and 52, and magneticcontactors 43, 44 and 45 will be in such position as to supply fullpower to the electrode chamber, as described in the previous method ofstarting.

As soon as the milk contacts-at electrode 69, circuit will beestablished from 2 la through relay 4|, through 40 to ground, causingrelay ll to act and open the pump circuit. This will stop the flow ofmilk and cause it to flow back by gravity through the heating chamberwhere it is further treated by areduced current through resistances 26,25 and 27, as previously described.

As soon as all of the milk, that attempted to pass, has returned to thechamber, circuit from electrode MI to ground will be broken and relay 4|will close the circuit through the pump and cause it to start throwingthe milk up to electrode 40 and bulb 22. If the temperature has not yetreached the pump will again stop and the milkwill be returned, aspreviously described. The pump will then again start and another testwill be made on temperature, and if it has reached a temperature above160, the pump will continue in operation until the milk,

that was in the chamber and received the extra treatment, has passedthrough. This will again be followed by milk below 160 because of thefact that regeneration has not yet been established, and this second lotof milk will be retained in the electrode chamber until it reaches theproper pasteurizing point, as previously described, and this operationcontinues until finally enough milk has been permitted to pass toestablish regeneration and bring the regenerative temperature upsufficiently high to permit continuous operation. The plant will then gointo normal continuous operation until all of the milk has beenpasteurized.

The process of shutting down is practically the same as in the previousmethod except that fresh water may be used to drive the milk out of thesystem.

I claim:

1. In a pasteurizing system, a liquid circulating system including aheating chamber having electrodes and a liquid heated preheater, a motordriven pump for forcing a liquid through said circulating system,manually controlled means for synchronizing the rate of flow of theliquid with the demand of a bottling machine, means for applying analternating current to the electrodes for heating the liquid forcedthrough the heating chamber, means for increasing and decreasing thevalue of the current passing through the heating chamber including anumber of resistances, one of which is normally in the heating circuit,and the others out of the heating circult, means controlled by thetemperature of the and decreasing the value of the current passingthrough the heating chamber, said means including a number ofresistances, one of which is normally in the heating circuit, the othersnormally out of the heating circuit, means controlled by the temperatureof the heated milk for starting and stopping the operation of the pumpwhen the temperature is varied a certain amount and cutting any or allof the resistances into or out of the heating circuit.-

3. In a pasteurizing apparatus, means for electrically heating a liquid,means for flowing the liquid through the heater, meansfor interruptingthe fiow of liquid through the heater when the'temperature of the liquidwhich has passed through the heater falls below a predetermined value,means enabling the liquid to be passed back through the heater, meansfor heat-. ing the liquid only a small amount on its back flow, meansfor automatically again passing the liquid through the heater when itsback flow has ceased, means for adjusting the rate of flow through theheater to the rate of operation of a bottling machine and means forcontrolling the temperature of liquid passing through the heater by achange of current in voltage on the heater to compensate for any changesin liquid temperature within a narrow range while the rate of liquidflow through the heater is maintained substantially constant.

4. A pasteurizing apparatus including an electric heater, means forpassing liquid through the heater at a substantially constant rate, acontinually operating make and brake device for cutting out resistancesin the heater circuit, and temperature responsive means for controllingthe time during which a resistance is in the heater circuit with respectto the time the resistance is out of the circuit, said make and breakdevice and the temperature responsive means being adapted to control thetemperature of the heated liquid within a fraction of a degree.

5, In a pasteurizing apparatus, a heater for liquid, means responsive tothe temperature of liquid flowing through the heater at a substantiallyconstant rate for intermittently increasing the voltage of the heaterwhen such temperature has fallen slightly below a normal pasteurizingtemperature, and temperature responsive means for intermittentlydecreasing the voltage of the heater when the liquid temperature risesslightly above said normal, the duration of the increase and decrease ofthe heater output being also responsive to the liquid temperature.

6. In a pasteurizing apparatus, a heater for liquid, a pump for passingthe liquid through the heater, means responsive to the temperature ofthe liquid after it has passed through the heater for increasing theheating of the liquid when its temperature drops slightly from a normalpasteurizing value and for reducing the power of the heater when theliquid temperature rises slightly above said normal value, meansresponsive to said last mentioned means for stopping the pump andre-passing the liquid through the heater when the temperature of theliquid which has passed the heater falls below a predetermined minimumwhich is below that for increasing the heating of the liquid, means forcooling the heaterduring its normal operation, and means for stoppingthe heating action of the heater in response to a reduction of saidcooling means.

7. In a pasteurizing system, a liquid circulating system including, aheating chamber having electrodes and a liquid-heated preheater, a motordriven pump for forcing liquid through said circulating system, manuallycontrolled means for synchronizing the rate of flow of the liquid withthe demand of a bottling machine, means for applying an alternatingcurrent to the electrodes for heating the liquid forced through theheating chamber, means for increasing and decreasing the value of thecurrent passing through the heating chamber including a number ofresistances, one of which is normally in the heating circuit, meanscontrolled by the temperature of the heated liquid for starting andstopping the operation of the pump when the temperature is varied acertain amount and cutting other resistances into and out of the heatingcircuit.

8. In a milk pasteurizing system, a liquid circulating system including,a heating chamber having water cooled electrodes and a milk-heatedpreheater, an electric motor driven pump for forcing milk throughsaidcirculating system, means for regulating the rate of flow of the milk,means for applying an alternating current to the electrodes for heatingthe milk forced through the heating chamber, means controlled by thetemperature of the heated milk for increasing and decreasing the valueof the current passing through the heating chamber, said means includinga number of resistances, one of which is normally in the heatingcircuit, means controlled by the temperature of the heated milk forstarting and stopping the operation of the pump when the temperature isvaried a certain amount and cutting the other resistances into and outof the heating circuit.

BENJAMIN E. GETCHELL.

